The proposed study examines the association between a taxometrically-derived anxiety sensitivity latent class variable (i.e., taxon) and vulnerability to panic psychopathology, indexed via panic-relevant responding to a well-established 10% carbon dioxide-enriched air (CO2) biological challenge, in a sample of 160 nonclinical college student participants. The main purposes of the proposed research are to (1) test the incremental predictive validity of the anxiety sensitivity taxon with respect to vulnerability for panic-relevant responding after parsing out the effect of other theoretically-relevant risk factors, and to (2) test whether a novel categorical model of anxiety sensitivity offers enhanced explanatory power relative to the pre-existing dimensional model. The proposed research is significant because it will help the field better understand cognitive vulnerability for panic-related problems and offers important clinically-relevant implications for the prevention/treatment of panic disorder. Moreover, the proposed project is innovative because it represents the first attempt to apply taxometric procedures to the experimental psychopathology study of panic vulnerability using a well-established biological challenge paradigm.